ABSTRACT (Lichtman) It is likely that abnormalities in the number or pattern of synaptic connections (?connectopathies?) underlie neurodevelopmental and psychiatric disorders such as autism spectrum disorder and schizophrenia. But finding pathological structural motifs in brain circuitry may require sufficient resolution to analyze each synapse and identify the networks linking thousands of pre- and postsynaptic neurons together. Such high resolution volumetric structural analysis can be achieved with serial section electron microscopy, however this process has been extremely slow and labor intensive preventing the comparison of samples and analysis of volumes containing multiple neurons. To solve these problems we have devised a largely automated computer and technology intensive pipeline to overcome the principal obstacles that have to date prevented discovering structural abnormalities in brain circuits. We propose to use this suite of automated microscopy and analysis tools to reconstruct circuits in insular or prefrontal cerebral cortex from mouse, marmoset and human (cerebral organoids and actual cerebral cortex). The aims are designed to provide synaptic and circuit level information about the effects of molecular perturbations being studied by other members of our Conte team. Each of these perturbations is associated with human neuropsychiatric and neurodevelopmental disorders. In all, 10 experimental brain tissues and their controls will be analyzed. We will take a structural inventory for a full thickness of cerebral cortex determining among other things: the number and types of neurons; the number and types of synapses; the synaptic vesicle numbers per synapse, mitochondrial numbers and densities per synapse; and sizes of active zones, dendritic spine number, density and size. In addition we will itemize the glial cell types, their prevalence, and look for differences is glial cell structure. All of these approaches have been used previously by us. Finally we will reconstruct circuits using a seed cell approach that we have also previously developed. It is our hope that providing this kind of detailed synaptic and connectional information for many abnormal and control tissue will help focus research on the sites of physical abnormality in diseases that to date have little in the way structural underpinnings.